The GSM system is a narrow-band communication system, a bandwidth of which is about 200 kHz. When GSM systems are used to form a cellular network, different frequency points can be used between possibly interfering neighbour cells, so as to avoid co-channel interference. A specific application is that several continuous frequency points (for example, these continuous frequency points occupy a bandwidth of 10 MHz) can be used during GSM networking, however, each cell only uses one or a few frequency points and frequency points used by a current cell and frequency points used by neighbour cells possibly interfering with the current cell are different, so that the co-channel interference is reduced. The LTE system is a wideband communication system, the bandwidth of which is configurable, and the bandwidth of one carrier can range from 1.4 MHz to 20 MHz.
It can be seen from the above description that each cell of the GSM system only occupies one or a few frequency points and the bandwidth used by each cell is very low compared to the total bandwidth (for example, if one cell only deploys one GSM frequency point and the available total bandwidth is 10 MHz, then the frequency spectrum utilization is only 0.2%).
Additionally, how to transit from frequency spectrums occupied by the GSM system to the LTE system smoothly also needs to be considered. An existing solution is to deploy vacated continuous frequency spectrum to the LTE system after the considerable continuous frequency spectrums are vacated due to the decrease of the number of users of the GSM. However, such approach has disadvantages of low frequency spectrum utilization and poor smoothness.
Therefore, how to enable the GSM system and the LTE system to share the same frequency spectrum and how to enable the GSM system to transit to the LTE system smoothly while improving frequency spectrum utilization become present concerns.